The present invention relates to an aggregate for delivering fuel from a fuel supply tank to an internal combustion engine of a motor vehicle.
Fuel-delivery aggregates of the type under discussion have been known. DE-OS No. 3,327,453 discloses a fuel supply aggregate in which a one-stage feeding pump is a gear pump (geromotor pump). Particularly during the fuel delivery of heated fuels (hot benzene problems can occur in the suction region of the pump, which would reduce pressure of the fluid in this region. This results in the formation of damping blows (cavitation), which in extreme cases can lead to the fact that the pump would not suck a sufficient amount of fuel or would be totally idle. This can also cause the danger of an improper vehicle operation. It has been found out that this problem is even worse, and practically un-controllable, with positive displacement pumps, and therefore the positive displacement pumps have been coupled to vented regenerative-type pumps. The so-arranged positive displacement pump has been fed with degassed fuel so that the problem of shielding has no longer occurred. A further advantage of such an arrangement resides in that operation noises have been reduced also in the case of higher temperatures and higher suction speeds because no cavitation has taken place in the pump chamber of the positive displacement pump. At the same time common wear is reduced by cavitation.